GMRT 610-MHz observations of the faint radio source population - and what these tell us about the higher radio-frequency sky
GMRT 610-MHz observations of the faint radio source population - and what these tell us about the higher radio-frequency sky
复制标题
GMRT 610-MHz 对微弱射电源群的观测——以及这些观测结果告诉我们关于更高无线电频率天空的信息
DOI：
10.1093/mnras/stw2638
复制
发表时间：
2017
影响因子：
4.8
通讯作者：
Whittam I
中科院分区：
文献类型：
--
作者：
Whittam I
在15.7千兆赫的第十次剑桥(10C)调查中，选取了96个微弱(S和GT；约0.5mJy)射电星系的完整样本。利用光谱将17个源分类为高激发或低激发射电星系(分别为HERGs和LERGs)，对其余的源使用其他三种方法：光学紧凑度、X射线观测和中红外彩色图解。32个来源是HERG，35个是LERG，其余29个来源无法分类。我们发现，与LERG相比，10C HERG具有更高的15.7 GHz磁通密度、更平坦的光谱、更小的线尺寸和更高的红移。这表明10C的HERG比LERG更具核心主导性。使用低频射电图像、线性尺寸和频谱指数根据射电形态对源进行分类；18个是Fanaroff和Riley I型或II型源，另外13个显示一些扩展发射，其余65个源是紧凑源，称为FR0源。FR0源被细分为紧凑的陡谱源(13个源)或千兆赫峰值的谱源(10个源)，其余42个属于非保密类别。FR0源在通量密度为15.7 GHz的子集中占主导地位，这与先前的结果一致，即较弱的10C源具有更平坦的射电频谱。将10C源的特性与更高通量密度的澳大利亚望远镜20 GHz(AT20G)调查进行了比较。10C源的红移与AT20G源相似，但亮度较低。高频选择的天体的性质随着通量密度的降低而改变；在高通量密度时，这些天体主要是类星体，而在低通量密度时，射电星系占主导地位。
A complete sample of 96 faint (S> 0.5 mJy) radio galaxies is selected from the Tenth Cambridge (10C) survey at 15.7 GHz. Optical spectra are used to classify 17 of the sources as high-excitation or low-excitation radio galaxies (HERGs and LERGs, respectively), for the remaining sources three other methods are used; these are optical compactness, X-ray observations and mid-infrared colour–colour diagrams. 32 sources are HERGs and 35 are LERGs while the remaining 29 sources could not be classified. We find that the 10C HERGs tend to have higher 15.7-GHz flux densities, flatter spectra, smaller linear sizes and be found at higher redshifts than the LERGs. This suggests that the 10C HERGs are more core dominated than the LERGs. Lower-frequency radio images, linear sizes and spectral indices are used to classify the sources according to their radio morphology; 18 are Fanaroff and Riley type I or II sources, a further 13 show some extended emission, and the remaining 65 sources are compact and are referred to as FR0 sources. The FR0 sources are sub-divided into compact, steep-spectrum sources (13 sources) or gigahertz-peaked spectrum sources (10 sources) with the remaining 42 in an unclassified class. FR0 sources are more dominant in the subset of sources with 15.7-GHz flux densities <1 mJy, consistent with the previous result that the fainter 10C sources have flatter radio spectra. The properties of the 10C sources are compared to the higher-flux density Australia Telescope 20 GHz (AT20G) survey. The 10C sources are found at similar redshifts to the AT20G sources but have lower luminosities. The nature of the high-frequency selected objects changes as flux density decreases; at high flux densities the objects are primarily quasars, while at low flux densities radio galaxies dominate.